The goal of this work is to understand the genetic and developmental underpinnings of organ morphogenesis. In this study, we focus on the problem of looping morphogenesis using the developing midgut as a model system. We previously demonstrated that the chirality of gut rotation (i.e. specification of its rotation in a counterclockwise direction) is mediated by changes in the cellular architecture of the dorsal mesentery. We have identified a number of transcription factors asymmetrically expressed in the dorsal mesentery. In the first Aim we will investigate the role each plays in changing the cellular organization within the mesentery as well as examining their cross regulation to understand the transcriptional network controlling this by first step of gut morphogenesis. In our second Aim we will turn our attention to the later steps of gut morphogenesis. We will examine how each subsequent coiling event relates to the initial decision to coil counter clockwise. We will examine the later roles of specific transcription factors in the process. And we will dissect the roles of physical forces and topological constraints in directing the formation of specific loops during midgut organogenesis. PUBLIC HEALTH RELEVANCE: We are studying looping morphogenesis of the gut. Failure in this process results in serious congenital malformations that, if left uncorrected, can lead to blockage of the GI tract, intestinal necrosis and death. There are also broader implications extending to an understanding of cardiac malformations, as looping morphogenesis is not well understood for any tubal organ, and parallels between the primitive gut tube and its dorsal mesentery with early heart tube and its dorsal mesocardium suggest similar biomechanisms may be involved.